Package irradiation systems



F Oct. 26, 1965 s. JEFFERSON PACKAGE IRRADIATION SYSTEMS Filed Dec. 14, 1961 United States Patent Ofitice 3,214,582 Patented Oct. 26, 1965 3,214,582 PACKAGE IRRADIATION SYSTEMS Sidney Jefierson, Abingdon, England, assignor to United Kingdom Atomic Energy Authority, London, England Filed Dec. 14, 1961, Ser. No. 159,380 Claims priority, application Great Britain, Dec. 30, 1960, 44,853/ 60 7 Claims. (Cl. 250-52) This invention relates to package irradiation systems and in particular to a system in which trolleys, suspended on an overhead railway, are used to convey packages past a radiation source. Such a system is described in the provisional specification which accompanies our co-pencling patent application No. 83,054, now US. Patent No. 3,142,759.

The radiation source is necessarily enclosed within a biological shield, which is generally of concrete, and the interior of the shield forms an irradiation cell. In known systems, trolleys containing packages of the materials to .be irradiated are passed through the shield by means of labyrinthine passageways to prevent radiation shine at the entry and exit points of the cell, but this method is disadvantageous in that the thickness of the shield must be increased to accommodate the passageways. Furthermore the vertical height of the openings required in the shield for the passage of a suspended trolley provide difficulties in that large openings permit unauthorised access to the interior of the cell and add to the number of interlocks required for the safe operation of the irradiation system.

The object of the present invention is to provide a package irradiation system in which the areas of the openings through which the packages enter and leave the irradiation cell are minimised and the construction of the biological shield simplified.

According to the invention a package irradiation system comprises a railway for conveying packages on trolleys past a radioactive source and lift means fer vertically moving said trolleys through an aperture formed in a biological shield surrounding said source.

The lift means comprises a moveable section of said railway which alternately aligns with fixed portions of railway within and without said shield.

Preferably each end of the lift means forms a radiation shielding plug for the aperture, the upper end of the lift closing the aperture when the lift means is in its lowermost-position and the lower end closing the aperture when the lift means is in its uppermost position.

To enable the nature of the invention to be more readily understood reference is directed to the accompanying drawing which illustrates one embodiment of the invention by way of example. In the drawings:

FIG. 1 is a diagrammatic plan of part of a biological shield and irradiation cell.

FIG. 2 is a vertical sectional elevation on the line II-II of FIG. 1.

Referring to the drawing, a biological shield 1 encloses a plate like gamma radiation source 2 to form an irradiation cell 3. An overhead rail track 4 is arranged within the cell such that a trolley 5 suspended from the rail track will make a succession of movement across both faces of the source 2 while passing through the cell. Each trolley is conveyed to and from the cell 3 by rail tracks 6 and 7 located outside and above the shield 1 and enters and leaves the cell 3 via suitable apertures 8 and 9 formed in a roof portion 10 of the shield.

In operation, a closely spaced succession of trolleys 5, each containing three packages 26, is fed into and withdrawn from the cell 3 through apertures 8 and respectively. The trolleys pass through apertures 8 and 9 by means of two lifts 11 and 12 vertically .moveable in the said apertures. The lifts are provided with a radiation shield 13 at their upper and lower ends. The upper end of each lift acts as a plug for the aperture when the lift is inside the cell and the lower nd provides a plug when the lift is outside the cell.

On each of the lifts, a short length of railway track 15 is positioned just below the radiation shield 13 at the upper end. This short length of track is alternately aligned with the railway track outside the cell and the railway track 4 inside the cell.

The operating mechanism for the lifts comprises a single chain 14 which passes around pulleys 16, 17 and 18 and is attached to each lift. The chain is driven by an electric or hydraulic motor 19 through a sprocket 21 The driving power required is relatively small as the lifts are balanced in operation. Correct alignment of the railway tracks is ensured by providing stops 21 and 22 within the cell, or alternatively, well known conventional methods may be used to control the movement of the chain and the power supply to the motor.

By correctly phasing the movements of the lifts with the movement of the trolleys past the source 2 a close succession of trolleys 5 may be passed through the cell 3.

The trolleys are moved by a conventional push rod mechanism (not shown) and the lifts are arranged such that a standard push rod stroke is required to transfer trolleys on to and off the moveable railway tracks 15. The cycle of movement is such that when a trolley 5 containing packages to be irradiated is being transferred from railway track 6 to the awaiting lift 11 positioned above entry aperture 8, a trolley 5, containing packages already irradiated, is being transferred from railway track 4 on to lift 12 waiting below the exit aperture 9. In a similar manner when the positions of the lifts 11 and 12 are interchanged by movement of chain 14, a trolley containing irradiated packages is transferred from lift 12 on to railway track 7 at the same instant as a trolley containing packages to be irradiated, is transferred from lift 11 on to railway track 4 inside the cell.

The addition of a collar 23 of shielding material of suitable density above and below each aperture can be used to increase the effective shielding in the neighborhood of the apertures. It is also advantageous to position the source 2 relative to the apertures such that paths of direct gamma radiation, as illustrated by lines 24 (FIG. 2), must impinge on a thickness of shielding material at least equivalent to the thickness of the biological shield 1.

Since the apertures 8 and 9 do not look directly at the source 2 the radiation shields 13 at the upper and lower ends of the lifts 11 and 12 need not be as thick as the roof 6 of the shield 11, even though the shields 13 are constructed of the same material. However if it is desired to increase the effective radiation shielding attached to each lift the radiation shields 13 may be of composite construction. For example, the upper portion 25 of each shield 13 may be of a heavy metal, such as lead, and the lower portion 27 of concrete.

I claim:

1. A package irradiation system comprising:

(a) a railway for conveying packages on trolleys past a radioactive source,

(b) lift means for vertically moving said trolleys through an aperture formed in a biological shield surrounding said source,

(c) said lift means having a section of railway which alternately aligns with fixed portions of railway within and without the shield, and

((1) each end of the lift means being extended to form a radiation shield plug for the aperture whereby the upper extended end of the lift means closes the aperture when the lift means is in its lowermost position and the lower extended end closes the aperture when the lift means is in its uppermost position.

2. A package irradiation system comprising:

(a) a railway for conveying packages on trolleys past a radioactive source (b) lift means for vertically moving said trolleys through an aperture formed in a biological shield surrounding said source,

(0) said lift means having a section of railway which alternately aligns with fixed portions of railway within and without the shield,

(d) collars of radiation shielding material coaxially positioned above and below the aperture in associa tion with the shield, and

(e) each end of the lift means being extended to form a radiation shield plug for the aperture whereby the upper extended end of the lift means closes the aperture when the lift means is in its lowermost position and the lower extended end closes the aperture when the lift means is in its uppermost position.

3. A package irradiation system comprising:

a railway for conveying packages on trolleys past a radioactive source;

a pair of lift means for vertically moving said trolleys through apertures formed in a biological shield surrounding said source;

said lift means having a section of railway which alternately aligns with fixed portions of railway within and without the shield;

collars of radiation shielding material coaxially positioned above and below the aperture in association with the shield;

the ends of each lift means being extended to form a radiation shield plug for the aperture whereby the upper extended end of a lift means closes the aperture when the lift means is in its lowermost position and the lower extended end closes the aperture when the lift means is in its uppermost position;

an operating chain interconnecting each lift means;

and

drive means associated with said chain whereby the position of the lifts may be interchanged by movement of the chain.

4. A package irradiation apparatus comprising:

a radioactive source;

a biological shield surrounding said source, and having inlet and outlet apertures therein;

first railways leading to and from said inlet and outlet apertures, respectively, on the outside of said shield;

a second railway inside said shield leading from the vicinity of said inlet aperture to the vicinity of said outlet aperture for conveying packages on trolleys past said radioactive source;

at least one trolley for transporting packages on said first and second railways;

means for moving said trolley vertically through said apertures, said means including a section of railway which alternately aligns with fixed portions of railway within and without the shield;

said last mentioned means further including two radiation shield plugs longitudinally spaced apart rela tive to the longitudinal axes of each aperture such that one plug closes the aperture when the moving means is in its lowermost position and the other plug closes the aperture when the moving means is in its uppermost position.

5. A package irradiation system comprising:

a radioactive source;

a biological shield surrounding said source, and having an aperture therein;

a first railway on the outside of said shield leading to said aperture and terminating in the vicinity of said aperture;

a second railway inside said shield leading from the vicinity of said aperture for conveying packages on trolleys past said radioactive source;

at least one trolley for transporting packages on said first and second railways;

means for moving said trolley vertically through said aperture, said means including a section of railway which alternately aligns with fixed portions of railway within and without the shield;

said last mentioned means further including two radia tion shield plugs longitudinally spaced apart relative to the longitudinal axis of said aperture such that one plug closes the aperture when the moving means is in its lowermost position and the other plug closes the aperture when the moving means is in its uppermost position.

6. A package irradiation apparatus as recited in claim 5 wherein said aperture extends vertically through a wall of said biological shield;

said section of railway on said moving means being horizontally disposed to align alternately with the ends of said railways on the inside and outside of said biological shield;

said radiation shield plugs being disposed on said moving means respectively above and below said section of railway and of a size and configuration so as substantially to correspond with the size and configuration of said aperture.

7. A package irradiation apparatus as recited in claim 6 wherein said biological shield includes respectively inlet and outlet apertures;

railways on the outside of said biological shield terminating in the vicinity of each of said apertures;

said railway on the inside of said biological shield leading from the inlet aperture to the outlet aperture past said radioactive source;

moving means for moving said trolley through each of said apertures;

and means interconnecting said moving means for mov ing them simultaneously through said apertures but in opposite senses.

References Cited by the Examiner UNITED STATES PATENTS 2,489,918 11/49 Menges 25052 2,938,804 5/60 Gordon et al 250-495 3,031,394 4/62 McCorkle et al. 250l06 FOREIGN PATENTS 883,967 7/53 Germany.

OTHER REFERENCES Sterilization of Medical Supplies With Gamma Radiation by L. E. Brownell et al. from the Proceedings of the International Conference of the Peaceful Uses of Atomic Energy, vol. 15, pp. 258264.

RALPH G. NILSON, Primary Examiner. 

1. A PACKAGE IRRADIATION SYSTEM COMPRISING: (A) A RAILWAY FOR CONVEYING PACKAGES ON TROLLEYS PAST A RADIOACTIVE SOURCE, (B) LIFT MEANS FOR VERTICALLY MOVING SAID TROLLEYS THROUGH AN APERTURE FORMED IN A BIOLOGICAL SHIELD SURROUNDING SAID SOURCE, (C) SAID LIFT MEANS HAVING A SECTION OF RAILWAY WHICH ALTERNATELY ALIGNS WITH FIXED PORTIONS OF RAILWAY WITHIN AND WITHOUT THE SHIELD, AND (D) EACH END OF THE LIFT MEANS BEING EXTENDED TO FORM A RADIATION SHIELD PLUG FOR THE APERTURE WHEREBY THE UPPER EXTENDED END OF THE LIFT MEANS CLOSES THE APERTURE WHEN THE LIFT MEANS IS IN ITS LOWERMOST POSITION AND THE LOWER EXTENDED END CLOSES THE APERTURE WHEN THE LIFT MEANS IS IN ITS UPPERMOST POSITION. 